Republican senators assail Liu's record during a hearing on his nomination for an appeals court. The dispute portends a tough fight to fill the Supreme Court vacancy.

Reporting from Washington — In a portent of the potential battle this summer over the Supreme Court vacancy, Goodwin Liu, President Obama's choice for the 9th U.S. Circuit Court of Appeals in San Francisco, faced a fusillade of criticism Friday from Senate Republicans who questioned his fitness for the bench.

Liu, 39, a law professor at UC Berkeley, is considered among the most liberal of Obama's judicial nominees. Republicans appear poised to oppose him, but they are also using his nomination to telegraph their concerns about the president's impending pick to replace retiring Supreme Court Justice John Paul Stevens.

Sen. Jeff Sessions (R-Ala.), the top Republican on the Senate Judiciary Committee, called Liu "the very vanguard of what I would call an intellectual judicial activist."

The GOP views Liu's nomination as part of a larger struggle over the future direction of the federal judiciary, and senators Friday repeatedly suggested that Liu would create new rights under the Constitution or apply the law in a biased manner. Their arguments echoed many of the criticisms directed at Supreme Court Justice Sonia Sotomayor during her confirmation hearing last year.

Republicans also pointed to Liu's lack of judicial experience. He has never been a judge and has argued few cases in court. Democrats praised Liu as a nominee whose credentials and background are unassailable -- and pointed out that two dozen George W. Bush administration nominees had also never been judges.

Liu is a former Rhodes scholar with an undergraduate degree from Stanford University and a law degree from Yale Law School. He sits on Stanford's Board of Trustees.

Like Sotomayor last year, Liu portrayed himself as bound by judicial precedent -- court rulings in previous cases -- and said there was no room for a judge to insert personal views into a case.

"I would approach every case with an open mind," he told the panel. "The role of a judge is to faithfully follow the law as it is written."

Liu struggled to reconcile some of his writings with that role. He has criticized conservative legal doctrine, written that the interpretation of the Constitution must evolve and adapt to a changing society, and theorized that people may have a constitutional right to "welfare" benefits, such as education and shelter, if those things are bestowed on them by legislative action.

"Whatever I may have written in books or in articles would have no bearing on my role as a judge," Liu said.

Liu testified before the committee in 2006 in opposition to Alito's confirmation. "Judge Alito's record envisions an America where police may shoot and kill an unarmed boy to stop him from running away with a stolen purse . . . where a black man may be sentenced to death by an all-white jury for killing a white man," Liu said then. "I humbly submit that this is not the America we know. Nor is it the America we aspire to be."

Kyl called Liu's remarks "vicious, emotionally and racially charged, very intemperate," and said they called into question Liu's capacity for fairness.

Liu responded that he had used "unnecessarily colorful language" in his testimony.

The hearing was dominated by Republicans, but they ultimately hold little sway on a committee on which Democrats outnumber them 12 to seven. That means Liu is likely to receive the panel's stamp of approval as early as next month.

But Democrats would probably need 60 votes to move Liu's nomination to a floor vote, and the conflict could consume substantial time on an already crowded Senate calendar.